An earlier version of a machine for dispensing stackable roofing washers individually from a stack of such washers and for driving fasteners through such washers is exemplified in Beach et al. U.S. Pat. Nos. 4,890,968, 5,042,142, and 5,056,684. A later version of such a machine is exemplified in Beach et al. U.S. Pat. Nos. 5,347,707, 5,445,297, and 5,555,780.
Generally, as known from at least some of the aforementioned Beach et al. patents, such a machine comprises a screw gun and an driving bit, which is mounted operatively to the screw gun and which is adapted to be rotatably driven by the screw gun and to drive a fastener rotatably when engaged with the fastener and driven by the screw gun.
Moreover, as known from at least some of the aforementioned Beach et al. patents, such a machine comprises a base, an upper, upright, tubular member having an upper end and mounting the screw gun at the upper end with the driving bit extending downwardly through the upper member, a middle, upright, tubular member having an upper end fitting inside the upper member, and a lower, upright, tubular member having an upper end fitting inside the middle member and a lower end mounted operatively to the base. The upper member is telescoped over the middle member and the middle member is telescoped over the lower member with the driving bit extending into the lower member.
Thus, the upper member is movable upwardly and downwardly over a limited range of vertical movement relative to the middle member, and the middle member is movable upwardly and downwardly over a limited range of vertical movement relative to the lower member. The tubular members of the machine are operated between a fully extended state where the upper and middle members are in their upper positions, wherein the driving bit does not extend through the lower end of the lower member, and a fully compressed state where the upper and middle members are biased to their lower positions, wherein the driving bit extends through the lower end of the lower member. The upper and middle members are biased to the fully extended state but are movable to the fully compressed state when the screw gun is depressed.
Furthermore, as known from at least some of the aforementioned Beach et al. patents, such a machine comprises a fastener-feeding tube, which is mounted operatively to the middle member and which is adapted to be vertically movable with the middle member, to receive a fastener if the fastener is dropped into an upper end of the fastener-feeding tube so that the shank of the fastener precedes the head of the fastener, and to guide the fastener into the lower member, below the driving bit, when the upper member is moved to the lower position.
Generally, as known from at least some of the aforementioned Beach et al. patents, such a machine comprises a magazine, which is integrated with the base, which is adapted to receive a stack of said washers inserted through an upper aperture of the magazine, to hold the stack, and to allow a lowermost washer in the stack to be laterally displaced from a lower region of the magazine, and which has two side walls spaced from each other.
Moreover, as known from at least some of the aforementioned Beach et al. patents, such a machine has a shuttle, which is adapted to be reciprocatingly driven between a washer-engaging position wherein a transverse rib of the shuttle engages the lowermost washer of the stack and a washer-releasing position wherein the shuttle releases the last-mentioned washer, and a transverse brace disposed across the shuttle, fixed to the shuttle by at least one fastener, and having a pivot pin at each end of the transverse brace. Thus, when the shuttle is driven between the washer-engaging and washer-releasing position, the fastener is stressed. Also, as the machine is used, the transverse rib tends to become worn.
Fastener-driving machines of related interest (without washer-dispensing capability) are exemplified in Murray U.S. Pat. No. 3,960,191 and in Dewey U.S. Pat. Nos. 4,236,555 and 4,397,412.